The present invention relates to a power-supply unit having a power supply controlling the voltage of a battery mounted on a vehicle.
In a so-called no-idling vehicle in which idling stop control is performed such that the engine of the vehicle is automatically stopped and started in accordance with operating state of the vehicle, the engine repeats restarting. Such no-idling vehicle is equipped with an auxiliary power supply for providing the voltage required for operating electric parts such as automotive audio equipment and a vehicle navigation system thereby to prevent the electric parts from malfunctioning or being reset due to a battery voltage drop at a restart of the engine. As an example of such power supply, Japanese Patent Application Publication 2005-237149 discloses a power supply that provides voltage boosted by turning on and off switching elements to electric parts at a restart of the engine and provides voltage to the electric parts through coils and diodes in the power supply without turning on and off the switching elements during normal operation of the vehicle except restarting of the engine.
As another example of such power supply, Japanese Patent Application Publication H09-277840 discloses a power supply in which the voltage of battery of an electric vehicle is stepped down and then supplied to auxiliary electric parts of the vehicle.
The power supply is large in size and also heavy, so that, in fixing the power supply to a vehicle by bolts and brackets, the vehicle needs have therein an extra space for receiving power supply and the degree of freedom in designing the vehicle decreases.
The present invention is directed to providing a power-supply unit and a power supply which prevents a decrease of the degree of freedom in designing a vehicle in consideration of mounting a power supply other than the battery to the vehicle.